Many devices utilize mercury in their operation, particularly in the field of electric lamps and lighting. Such devices include arc discharge lamps which typically employ mercury as one of the vaporizable components therein. See, for example, Waymouth, Electric Discharge Lamps, MIT Press 1971 for a description of the basic principles of such lamps.
In U.S. Pat. No. 4,379,252, (the '252 patent), the advantages of utilizing higher than normal levels of .sup.196 Hg in the Hg added to fluorescent lamps are described and include unexpectedly high efficiency gains in light output. The disclosure of this patent is hereby incorporated herein by reference.
The drawback of using this isotope lies in its high cost. For example, using conventional enrichment techniques, mercury which has been enhanced to contain about 35% of the .sup.196 Hg isotope can cost about $500 per milligram. While only sub-milligram quantities of this isotope need be added to a fluorescent lamp to afford beneficial results, economic realities always play a part in consumer products. Accordingly, it is easy to understand why more economical methods of obtaining this isotope continue to be sought.
Isotopically enriched mercury can be produced by a number of methods. One method involves photosensitized chemical reactions utilizing elemental mercury and various compounds. For example, the compounds HCl and O.sub.2 react with mercury atoms when the mercury atoms are excited by resonance radiation, in particular, 2537.ANG. radiation produced in a Hg (.sup.3 P-.sup.1 S.sub.o) transition generating isotopically selective reactions. Thus, the Hg compound formed contains Hg enriched in a particular isotope, and the Hg must be separated from the compound into its liquid or free state (i.e., elemental Hg)) in order to recover the isotopically enriched metal.
Product formation in the reaction: EQU .sup.196 Hg (6.sup.3 P)+HCl.fwdarw..sup.196 HgCl+H
which is used for .sup.196 Hg isotope separation, can lend to a "photon starved" process after a short period (e.g., one to two hours of operation). One way of avoiding this is to use a nested group of reactors, each with a common longitudinal axis. Product formation first takes place in the outermost nested vessel until "photon starvation" begins, then the next innermost chamber is used. Nesting with at least three levels significantly reduces floor space and reactor system size requirements.
The present invention is thus directed to such a nested reactor and to the process of using such a reactor for the photochemical enrichment of mercury.